Method for making patterned conductive element

ABSTRACT

The present disclosure relates to a method for making pattern conductive element. The method includes steps. A substrate having a surface is provide. An adhesive layer is formed on the surface of the substrate. Part of the adhesive layer is solidified to form a solidified adhesive layer and a non-solidified adhesive layer. A carbon nanotube layer is applied on the adhesive layer. The non-solidified adhesive layer is solidified so that the carbon nanotube layer on the non-solidified adhesive layer forms a fixed carbon nanotube layer and the carbon nanotube layer on the solidified adhesive layer forms a non-fixed carbon nanotube layer. The non-fixed carbon nanotube layer is removed and the fixed carbon nanotube layer is remained to form a pattern carbon nanotube layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims all benefits accruing under 35 U.S.C. §119 fromTaiwan Patent Application No. 100120203, filed on Jun. 9, 2011, in theTaiwan Intellectual Property Office, the contents of which are herebyincorporated by reference. This application is related to applicationsentitled, “TOUCH PANEL”, filed Dec. 29, 2011 ( Ser. No. 13/339,643); and“METHOD FOR MAKING TOUCH PANEL”, filed Dec. 29, 2011(Ser. No.13/339,658); and “METHOD FOR MAKING TOUCH PANEL”, filed Dec. 29, 2011(Ser. No. 13/339,664); and “METHOD FOR MAKING TOUCH PANEL”, filed Dec.29, 2011 (Ser. No. 13/339,671); and “TOUCH PANEL AND METHOD FOR MAKINGTHE SAME”, filed Dec. 29, 2011 (Ser. No. 13/339,678); and “METHOD FORMAKING TOUCH PANEL”, filed Dec. 29, 2011 (Ser. No. 13/339,681); and“METHOD FOR MAKING TOUCH PANEL”, filed Dec. 29, 2011 (Ser. No.13/339,688); and “PATTERNED CONDUCTIVE ELEMENT”, filed Dec. 29, 2011(Ser. No. 13/339,696); and “METHOD FOR MAKING PATTERNED CONDUCTIVEELEMENT”, filed Dec. 29, 2011 (Ser. No. 13/339,700); and “TOUCH PANEL”,filed Dec, 29, 2011 (Ser. No. 13/339,709); and “TOUCH PANEL”, filed Dec.29, 2011 (Ser. No. 13/339,718).

BACKGROUND

1. Technical Field

The present disclosure relates to patterned conductive elements andmethod for making the same, particularly, to a carbon nanotube basedpatterned conductive element and a method for making the same.

2. Description of Related Art

Patterned conductive elements, especially patterned transparentconductive elements, are widely used in the electronic devices such as atouch screen, a liquid crystal display (LCD), or a field emissiondisplay (FED).

A conventional patterned transparent conductive element includes apatterned transparent conductive indium tin oxide (ITO). However, theITO layer has poor wearability, low chemical endurance and unevenresistance in an entire area of the panel. Furthermore, the ITO layer isgenerally formed by means of ion-beam sputtering and etched by laserbeam, and the method is relatively complicated.

What is needed, therefore, is to provide a patterned conductive elementand a method for making the same which can overcome the shortcomingdescribed above.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the embodiments can be better understood with referenceto the following drawings. The components in the drawings are notnecessarily drawn to scale, the emphasis instead being placed uponclearly illustrating the principles of the embodiments. Moreover, in thedrawings, like reference numerals designate corresponding partsthroughout the several views.

FIG. 1 is a schematic view of one embodiment of a patterned conductiveelement.

FIG. 2 is an enlargement view of the part II-II of FIG. 1.

FIG. 3 is a schematic, top view of one embodiment of a patternedconductive element.

FIG. 4 is a schematic, top view of another embodiment of a patternedconductive element.

FIG. 5 is a flowchart of one embodiment of a method for making apatterned conductive element.

FIG. 6 is a schematic, top view of an adhesive layer having a solidifiedadhesive layer and a non-solidified adhesive layer.

FIG. 7 is a Scanning Electron Microscope (SEM) image of a carbonnanotube film.

DETAILED DESCRIPTION

The disclosure is illustrated by way of example and not by way oflimitation in the figures of the accompanying drawings in which likereferences indicate similar elements. It should be noted that referencesto “an” or “one” embodiment in this disclosure are not necessarily tothe same embodiment, and such references mean at least one.

References will now be made to the drawings to describe, in detail,various embodiments of the present patterned conductive elements andmethods for making the same.

Referring to FIG. 1, a patterned conductive element 10 of one embodimentincludes a substrate 12, an adhesive layer 13, and a patterned carbonnanotube layer 18.

The substrate 12 can be flat or curved and configured to support otherelements. The substrate 12 can be insulative and transparent, opaque, ortranslucent.

In one embodiment, the transmittance of the substrate 12 can be greaterthan 75%. The substrate 12 can be made of rigid materials such assilicon, ceramic, glass, quartz, diamond, plastic or any other suitablematerial. The substrate 12 can also be made of flexible materials suchas polycarbonate (PC), polymethyl methacrylate acrylic (PMMA), polyimide(PI), polyethylene terephthalate (PET), polyethylene (PE), polyetherpolysulfones (PES), polyvinyl polychloride (PVC), benzocyclobutenes(BCB), polyesters, or acrylic resin. In one embodiment, the substrate 12is a flat and flexible PET plate.

The adhesive layer 13 is configured to fix the patterned carbon nanotubelayer 18 on the substrate 12. The adhesive layer 13 can be transparent,opaque, or translucent. In one embodiment, the transmittance of theadhesive layer 13 can be greater than 75%. The adhesive layer 13 can bemade of materials such as hot plastic or UV (Ultraviolet Rays) glue, forexample PVC or PMMA. The thickness of the adhesive layer 13 can be in arange from about 1 nanometer to about 500 micrometers, for example, thethickness is in a range from about 1 micrometer to about 2 micrometers.In one embodiment, the adhesive layer 13 is a UV glue layer with athickness of 1.5 micrometers.

The patterned carbon nanotube layer 18 can be a continuous structure orincludes a plurality of spaced carbon nanotube patterns arranged in theform of an array. The plurality of carbon nanotube patterns can behexagonally arranged, squarely arranged, or concentrically arranged. Thecarbon nanotube pattern can be a triangle, parallelogram, diamond,square, trapezoid, rectangle, or circle. In one embodiment, thepatterned carbon nanotube layer 18 includes a plurality of carbonnanotube patterns having the same shape as shown in FIG. 3. In oneembodiment, the patterned carbon nanotube layer 18 includes a pluralityof carbon nanotube patterns having different shapes as shown in FIG. 4.

Further referring to FIG. 2, the patterned carbon nanotube layer 18includes a plurality of carbon nanotubes 182. The carbon nanotubes 182in each carbon nanotube pattern are joined end-to-end by van der Waalsattractive force therebetween to form an integral structure. A majorityof the carbon nanotubes 182 are arranged to extend along the directionsubstantially parallel to the surface of the adhesive layer 13. Aplurality of gaps is defined between adjacent carbon nanotubes 182 sothat part of the adhesive layer 13 is exposed. The surface of theexposed adhesive layer 13 is substantially smooth. The plurality of gapsis filled with the adhesive layer 13, namely part of the adhesive layer13 permeates into the patterned carbon nanotube layer 18. The singlecarbon nanotube 182 can be entirely embedded in the adhesive layer 13.Also, the single carbon nanotube 182 can have a first part embedded inthe adhesive layer 13 and a second part exposed from the adhesive layer13. In one embodiment, each of the carbon nanotubes 182 extends along adirection substantially parallel to the surface of the adhesive layer 13and has a first part embedded in the adhesive layer 13 and a second partexposed from the adhesive layer 13.

The transmittance of the patterned carbon nanotube layer 18 can begreater than 75%. When the substrate 12, the adhesive layer 13, and thepatterned carbon nanotube layer 18 allow light to pass through, thepatterned conductive element 10 can be used as a transparent conductiveelement and applied in the electronic devices such as a touch screen, aLCD, or a FED.

Referring to FIG. 5, a method for making the patterned conductiveelement 10 of one embodiment includes the steps of:

-   -   step (S10), providing a substrate 12;    -   step (S20), applying an adhesive layer 13 on a surface of the        substrate 12;    -   step (S30), forming a solidified adhesive layer 132 and a        non-solidified adhesive layer 134 by partially solidifying the        adhesive layer 13;    -   step (S40), placing a carbon nanotube layer 14 on a surface of        the adhesive layer 13;    -   step (S50), solidifying the non-solidified adhesive layer 134 so        that the carbon nanotube layer 14 on the non-solidified adhesive        layer 134 forms a fixed carbon nanotube layer and the carbon        nanotube layer 14 on the solidified adhesive layer 132 forms a        non-fixed carbon nanotube layer; and    -   step (S60), removing the non-fixed carbon nanotube layer on the        solidified adhesive layer 132 to obtain a patterned carbon        nanotube layer 18.

In Step (S10), the Substrate 12 is a Pet Film.

In step (S20), the adhesive layer 13 can be any adhesive which can besolidified on a certain condition. The adhesive layer 13 is transparentand can be made of materials such as hot plastic or UV glue, for examplePVC or PMMA. The adhesive layer 13 can be formed by spin-coating,spraying, or brushing. In one embodiment, a UV glue layer with athickness of 1.5 micrometers is formed on the substrate 12 byspin-coating.

In step (S30), the method for solidifying the adhesive layer 13 dependson the material of the adhesive layer 13. The thermoplastic adhesivelayer 13 can be solidified by partially cooling, the thermosettingadhesive layer 13 can be solidified by partially heating by infraredradiation through a mask, and the UV glue adhesive layer 13 can besolidified by partially irradiating with ultraviolet light.

The non-solidified adhesive layer 134 has a pattern corresponding tothat of the patterned carbon nanotube layer 18. The non-solidifiedadhesive layer 134 includes a plurality of predetermined patterns. Thepredetermined pattern can be a triangle, parallelogram, diamond, square,trapezoid, rectangle, or circle.

Referring to FIG. 6, in one embodiment, the solidified adhesive layer132 includes a plurality of first stripes spaced from each other, andthe non-solidified adhesive layer 134 includes a plurality of secondstripes spaced from each other. The first stripes and second stripes arelocated alternately. The adhesive layer 13 is UV glue layer and can besolidified by steps of:

-   -   step (S301), sheltering the adhesive layer 13 by a mask 15;    -   step (S302), irradiating the adhesive layer 13 with ultraviolet        light 16; and    -   step (S303), removing the mask 15.

In step (S301), the mask 15 can be suspended above the adhesive layer13. The shape and area of the mask 15 can be selected according to thepatterned carbon nanotube layer 18. In one embodiment, the mask 15includes a body 150 defining a plurality of holes 152. The body 150 isused to block the ultraviolet light 16. The holes 152 can allow theultraviolet light 16 to pass through. In one embodiment, the mask 15 isa plate having a plurality of stripe-shaped openings.

In step (S302), the adhesive layer 13 can be irradiated for about 2seconds to about 30 seconds. In one embodiment, the adhesive layer 13 isirradiated for about 4 seconds. The adhesive layer 13 corresponding tothe holes 152 is solidified to form the solidified adhesive layer 132,and the adhesive layer 13 corresponding to the body 150 is notsolidified and forms the non-solidified adhesive layer 134.

In step (S40), the carbon nanotube layer 14 can be formed by transferprinting a preformed carbon nanotube film, filtering and depositing acarbon nanotube suspension, or laying a free-standing carbon nanotubefilm. In one embodiment, the carbon nanotube film is drawn from a carbonnanotube array and then placed on the adhesive layer 13 directly. Afterthe carbon nanotube layer 14 is placed on the adhesive layer 13, thecarbon nanotube layer 14 on the solidified adhesive layer 132 is onlylocated on surface of the solidified adhesive layer 132 and connectedwith the solidified adhesive layer 132 by van der Waals attractiveforce. The carbon nanotube layer 14 on the non-solidified adhesive layer134 is infiltrated into the non-solidified adhesive layer 134 and willbe fixed by the non-solidified adhesive layer 134 in following step(S50). In one embodiment, the carbon nanotube layer 14 on thenon-solidified adhesive layer 134 include a plurality of carbonnanotubes infiltrated into and extending out of the non-solidifiedadhesive layer 134. Furthermore, a step of pressing the carbon nanotubelayer 14 can be performed after step (S40) to allow more carbonnanotubes of the carbon nanotube layer 14 to infiltrate into thenon-solidified adhesive layer 134.

The carbon nanotube layer 14 includes a plurality of carbon nanotubes.The carbon nanotube layer 14 can be a substantially pure structure ofthe carbon nanotubes, with few impurities and chemical functionalgroups. A majority of the carbon nanotubes are arranged to extend alongthe direction substantially parallel to the surface of the carbonnanotube layer 14. The carbon nanotubes in the carbon nanotube layer 14can be single-walled, double-walled, or multi-walled carbon nanotubes.The length and diameter of the carbon nanotubes can be selectedaccording to need, for example the diameter can be in a range from about0.5 nanometers to about 50 nanometers and the length can be in a rangefrom about 200 nanometers to about 900 nanometers. The thickness of thecarbon nanotube layer 14 can be in a range from about 0.5 nanometers toabout 100 micrometers, for example in a range from about 100 nanometersto about 200 nanometers. The carbon nanotube layer 14 has a goodflexibility because of the good flexibility of the carbon nanotubestherein.

The carbon nanotubes of the carbon nanotube layer 14 can be arrangedorderly to form an ordered carbon nanotube structure or disorderly toform a disordered carbon nanotube structure. The term ‘disordered carbonnanotube structure’ includes, but is not limited to, to a structurewhere the carbon nanotubes are arranged along many different directions,and the aligning directions of the carbon nanotubes are random. Thenumber of the carbon nanotubes arranged along each different directioncan be almost the same (e.g. uniformly disordered). The carbon nanotubesin the disordered carbon nanotube structure can be entangled with eachother. The term ‘ordered carbon nanotube structure’ includes, but is notlimited to, a structure where the carbon nanotubes are arranged in aconsistently systematic manner, e.g., the carbon nanotubes are arrangedapproximately along a same direction and/or have two or more sectionswithin each of which the carbon nanotubes are arranged approximatelyalong a same direction (different sections can have differentdirections).

In one embodiment, the carbon nanotube layer 14 is a free-standingstructure. The term “free-standing structure” means that the carbonnanotube layer 14 can sustain the weight of itself when it is hoisted bya portion thereof without any significant damage to its structuralintegrity. Thus, the carbon nanotube layer 14 can be suspended by twospaced supports.

The carbon nanotube layer 14 includes at least one free-standing carbonnanotube film. The free-standing carbon nanotube film can be drawn froma carbon nanotube array and then placed on the patterned adhesive layer13 directly and easily. In one embodiment, the carbon nanotube film canbe made by the steps of: growing a carbon nanotube array on a wafer bychemical vapor deposition method; and drawing the carbon nanotubes ofthe carbon nanotube array to from the carbon nanotube film. During thedrawing step, the carbon nanotubes are joined end-to-end by van derWaals attractive force therebetween along the drawing direction. Thecarbon nanotube film has the smallest resistance along the drawingdirection and the greatest resistance along a direction perpendicular tothe drawing direction. Thus, the carbon nanotube film is resistanceanisotropy. Furthermore, the carbon nanotube film can be etched orirradiated by laser. After being irradiated by laser, a plurality ofparallel carbon nanotube conductive strings will be formed and theresistance anisotropy of the carbon nanotube film will not be damagedbecause the carbon nanotube substantially extending not along thedrawing direction are removed by burning. Each carbon nanotubeconductive string includes a plurality of carbon nanotubes joinedend-to-end by van der Waals attractive force.

In one embodiment, the carbon nanotube layer 14 is a single carbonnanotube film. The carbon nanotube film includes a plurality ofsuccessive and oriented carbon nanotubes joined end-to-end by van derWaals attractive force therebetween. The carbon nanotube film is afree-standing film. Referring to FIG. 7, each carbon nanotube filmincludes a plurality of successively oriented carbon nanotube segmentsjoined end-to-end by van der Waals attractive force therebetween. Eachcarbon nanotube segment includes a plurality of carbon nanotubesparallel to each other, and combined by van der Waals attractive forcetherebetween. Some variations can occur in the carbon nanotube film. Thecarbon nanotubes in the carbon nanotube film are oriented along apreferred orientation. The carbon nanotube film can be treated with anorganic solvent to increase the mechanical strength and toughness andreduce the coefficient of friction of the carbon nanotube film. Athickness of the carbon nanotube film can range from about 0.5nanometers to about 100 micrometers.

The carbon nanotube layer 14 can include at least two stacked carbonnanotube films. In other embodiments, the carbon nanotube layer 14 caninclude two or more coplanar carbon nanotube films. Additionally, whenthe carbon nanotubes in the carbon nanotube film are aligned along onepreferred orientation, an angle can exist between the orientations ofcarbon nanotubes in adjacent films, whether stacked or adjacent.Adjacent carbon nanotube films can be combined by only the van der Waalsattractive force therebetween. An angle between the aligned directionsof the carbon nanotubes in two adjacent carbon nanotube films can rangefrom about 0 degrees to about 90 degrees. When the angle between thealigned directions of the carbon nanotubes in adjacent stacked carbonnanotube films is larger than 0 degrees, a plurality of micropores isdefined by the carbon nanotube film. Stacking the carbon nanotube filmswill also add to the structural integrity of the carbon nanotube film.

In step (S50), the method for solidifying the non-solidified adhesivelayer 134 is same as the method for solidifying the adhesive layer 13provided in step (S30). Because the carbon nanotube layer 14 on thenon-solidified adhesive layer 134 is infiltrated into the non-solidifiedadhesive layer 134, the carbon nanotube layer 14 on the non-solidifiedadhesive layer 134 is fixed by the adhesive layer 13 to form the fixedcarbon nanotube layer in step (S50). The carbon nanotube layer 14 on thesolidified adhesive layer 132 will not be fixed by the adhesive layer 13and will form the non-fixed carbon nanotube layer. In one embodiment,the non-solidified adhesive layer 134 is solidified by irradiating withultraviolet light 16.

In step (S60), the non-fixed carbon nanotube layer on the solidifiedadhesive layer 132 can be removed by a method such as stripping by anadhesive tape or peeling by a roller having an adhesive outer surface.Because the bonding force between the non-fixed carbon nanotube layerand the solidified adhesive layer 132 is weak, the non-fixed carbonnanotube layer will be removed easily by the adhesive tape or the rollerhaving an adhesive outer surface. In one embodiment, the non-fixedcarbon nanotube layer is stripped by an adhesive tape. Compared to theprocess of forming ITO layer by ion-beam sputtering and etching ITOlayer by laser beam, the process of making the patterned carbon nanotubelayer 18 is simple and low cost. Furthermore, the non-fixed carbonnanotube layer can be removed by a method such as laser-beam etching,ion-beam etching, or electron-beam etching. The fixed carbon nanotubelayer on the will be remained to form the patterned carbon nanotubelayer 18.

It is to be understood that the above-described embodiments are intendedto illustrate rather than limit the disclosure. Any elements describedin accordance with any embodiments is understood that they can be usedin addition or substituted in other embodiments. Embodiments can also beused together. Variations may be made to the embodiments withoutdeparting from the spirit of the disclosure. The above-describedembodiments illustrate the scope of the disclosure but do not restrictthe scope of the disclosure.

Depending on the embodiment, certain of the steps of methods describedmay be removed, others may be added, and the sequence of steps may bealtered. It is also to be understood that the description and the claimsdrawn to a method may include some indication in reference to certainsteps. However, the indication used is only to be viewed foridentification purposes and not as a suggestion as to an order for thesteps.

What is claimed is:
 1. A method for making a patterned conductiveelement, the method comprising: providing a substrate; applying anadhesive layer on a surface of the substrate; forming a solidifiedadhesive layer and a non-solidified adhesive layer by partiallysolidifying the adhesive layer; placing a carbon nanotube layer on asurface of the adhesive layer; solidifying the non-solidified adhesivelayer so that the carbon nanotube layer on the non-solidified adhesivelayer forms a fixed carbon nanotube layer and the carbon nanotube layeron the solidified adhesive layer forms a non-fixed carbon nanotubelayer; and removing the non-fixed carbon nanotube layer to obtain apatterned carbon nanotube layer.
 2. The method of claim 1, wherein theadhesive layer is formed by spin-coating, spraying, or brushing.
 3. Themethod of claim 1, wherein the adhesive layer comprises thermoplasticand is solidified by cooling.
 4. The method of claim 1, wherein theadhesive layer comprises thermosetting material and is solidified byheating.
 5. The method of claim 1, wherein the adhesive layer comprisesUV glue and is solidified by ultraviolet light irradiating.
 6. Themethod of claim 5, wherein the partially solidifying the adhesive layercomprises: sheltering the adhesive layer by a mask; irradiating theadhesive layer with ultraviolet light; and removing the mask.
 7. Themethod of claim 6, wherein the mask is suspended above the adhesivelayer.
 8. The method of claim 1, wherein the carbon nanotube layer isformed by filtering and depositing a carbon nanotube suspension.
 9. Themethod of claim 1, wherein the carbon nanotube layer is formed bydrawing a free-standing carbon nanotube film from a carbon nanotubearray; and laying the free-standing carbon nanotube film on the adhesivelayer directly.
 10. The method of claim 9, wherein at least twofree-standing carbon nanotube films are stacked on the adhesive layer.11. The method of claim 1, wherein after applying the carbon nanotubelayer on the adhesive layer, the carbon nanotube layer on the solidifiedadhesive layer is only located on a surface of the solidified adhesivelayer, and the carbon nanotube layer on the non-solidified adhesivelayer is infiltrated into the non-solidified adhesive layer.
 12. Themethod of claim 11, wherein the carbon nanotube layer on thenon-solidified adhesive layer comprises a plurality of carbon nanotubesinfiltrated into and extending out of the non-solidified adhesive layer.13. The method of claim 1, further comprising pressing the carbonnanotube layer after applying the carbon nanotube layer on the adhesivelayer.
 14. The method of claim 1, wherein the non-fixed carbon nanotubelayer is removed by stripping using an adhesive tape.
 15. The method ofclaim 1, wherein the non-fixed carbon nanotube layer is removed bypeeling using a roller having an adhesive outer surface.
 16. The methodof claim 1, wherein the non-fixed carbon nanotube layer is removed bylaser-beam etching, ion-beam etching, or electron-beam etching.